(1) Field of the Invention
The present invention relates to a method of protecting seeds that are to be treated with a phytotoxic agent, and in particular, to a method for improving the germination rate of phytotoxic agent-treated seeds. Also included are seeds that have been treated by the subject method, and plants that grow from such seeds.
(2) Description of the Related Art
A significant fraction of plant seed is now treated with one or more agrochemicals, such as pesticides, inoculants, growth factors, and fertilizers, in order to control pests and diseases, to provide nutrients, stimulate germination, and enhance the growth of the seedling. Some of the agrochemicals that are useful in controlling pests and diseases can also be toxic to the seed and to the plant that sprouts from the seed. Such phytotoxic activity limits the amount of these agrochemicals that can safely be applied to the seed.
One undesirable effect of phytotoxicity is the reduction of the germination rate of seeds that have been treated. Typically, the germination rate of seeds that are treated with a phytotoxic agent decreases with time after the agent has been applied, thereby limiting the shelf life of the treated seeds. Sometimes extraordinary measures, such as in-field seed treatment, or treatment immediately before planting, are required to avoid serious damage to the crop. It has also been recognized that phytotoxic damage to seed by agrochemical agents may be exacerbated by exposure of the seed to environmental stresses, such as cold, drought, and the like.
Phytotoxicity of agrochemicals has been dealt with in several ways. The inclusion of safeners—chemicals which ameliorate the phytotoxic affects of agrochemicals, such as herbicides—along with the seed, is widely used, but this requires the application of an additional, often expensive, chemical component to the seed.
Another way to overcome the phytotoxic effect is to encapsulate the agrochemical agent in a matrix, often a polymer, which limits the movement of the agent. See, e.g., U.S. Pat. No. 6,329,319 to Puglisi et al. This method can limit the contact of the agent with the seed and the emerging seedling, while permitting the agent to become available later during germination and initial plant growth as the agent is released from the polymer matrix. The proper operation of encapsulation technology depends on careful matching of the physical and chemical properties of the agrochemical and the encapsulating matrix. Neither one polymer matrix, nor one encapsulation process, is suitable for encapsulation of all agrochemical agents now in use for seed treatment.
Agrochemical agents can also be included in seed coatings, which can limit the mobility of the agent. See, e.g., U.S. Pat. No. 6,199,318 to Stewart et al., U.S. Pat. No. 5,129,180 to Stewart, U.S. Pat. No. 5,127,185 to Kojimoto et al., U.S. Pat. No. 5,044,116 to Gago et al., and U.S. Pat. No. 3,947,906 to Watts. However, because the active agent is distributed throughout the coating, some finite amount of the agent, by necessity, comes in contact with the surface of the seed. Moreover, like encapsulation, the chemical and physical parameters of the matrix material must be matched with the properties of the active agent in order to obtain the proper homogeneity for the coating and to avoid cracking.
It is known to apply polymer coatings to seeds for the purpose of reducing imbibitional chilling injury. See, Ni, B—R, Alleviation of seed imibitional chilling injury using polymer film coating, British Crop Protection Council Symposium Proceedings, No. 76, Pp. 73-82 (2001); also, Taylor, A. G., Bean Improvement Cooperative, 30.30-31 (1987); Taylor et al., J. Horticultural Sci., 62:183-189 (1987); Taylor, A. G. and J. Kwiatkowski, Polymer film coatings decrease water uptake and water vapor movement into seeds and reduce imbibitional chilling injury, West et al., Crop Science, 25:941-944 (1985). But the combination of such coatings with subsequent seed treatment with phytotoxic agrochemicals was not described.
It would be useful, therefore, to provide a method for reducing phytotoxic injury to seeds from phytotoxic seed treatment agents, which method can be used with a broad range of agrochemical agents and applied to a broad range of seed types.